Characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding   总被引：2，自引：0，他引：2  

Marc Descloitres  Laurent Ruiz  M. Sekhar  Anatoly Legchenko  Jean‐Jacques Braun  M. S. Mohan Kumar  S. Subramanian 《水文研究》2008,22(3):384-394

A groundwater recharge process of heterogeneous hard rock aquifer in the Moole Hole experimental watershed, south India, is being studied to understand the groundwater flow behaviour. Significant seasonal variations in groundwater level are observed in boreholes located at the outlet area indicating that the recharge process is probably taking place below intermittent streams. In order to localize groundwater recharge zones and to optimize implementation of boreholes, a geophysical survey was carried out during and after the 2004 monsoon across the outlet zone. Magnetic resonance soundings (MRS) have been performed to characterize the aquifer and measure groundwater level depletion. The results of MRS are consistent with the observation in boreholes, but it suffers from degraded lateral resolution. A better resolution of the regolith/bedrock interface is achieved using electrical resistivity tomography (ERT). ERT results are confirmed by resistivity logging in the boreholes. ERT surveys have been carried out twice—before and during the monsoon—across the stream area. The major feature of recharge is revealed below the stream with a decrease by 80% of the calculated resistivity. The time‐lapse ERT also shows unexpected variations at a depth of 20 m below the slopes that could have been interpreted as a consequence of a deep seasonal water flow. However, in this area time‐lapse ERT does not match with borehole data. Numerical modelling shows that in the presence of a shallow water infiltration, an inversion artefact may take place thus limiting the reliability of time‐lapse ERT. A combination of ERT with MRS provides valuable information on structure and aquifer properties respectively, giving a clue for a conceptual model of the recharge process: infiltration takes place in the conductive fractured‐fissured part of the bedrock underlying the stream and clayey material present on both sides slows down its lateral dissipation. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Reventador Volcano 2005: Eruptive activity inferred from seismo-acoustic observation     

Jonathan M. Lees  Jeffrey B. Johnson  Mario Ruiz  Liliana Troncoso  Matt Welsh 《Journal of Volcanology and Geothermal Research》2008

Reventador Volcano entered an eruptive phase in 2005 which included a wide variety of seismic and infrasonic activity. These are described and illustrated: volcano-tectonic, harmonic tremor, drumbeats, chugging and spasmodic tremor, long period and very long period events. The recording of this simultaneous activity on an array of three broadband, seismo-acoustic instruments provides detailed information of the state of the conduit and vent during this phase of volcanic eruption. Quasi-periodic tremor at Reventador is similar to that observed at other volcanoes and may be used as an indicator of vent aperture. Variations in the vibration modes of the volcano, frequency fluctuations and rapid temporal fluctuations suggest the influx of new material, choking of the vent and possible modification of the conduit geometry during explosions and effusion over a period of six weeks.  相似文献   

Non-linear explosion tremor at Sangay,Volcano, Ecuador     

Jonathan M. Lees  Mario Ruiz 《Journal of Volcanology and Geothermal Research》2008

  相似文献   

Crustal structure in the Falcón Basin area, northwestern Venezuela, from seismic and gravimetric evidence     

Maximiliano J. Bezada  Michael Schmitz  María Ins Jcome  Josmat Rodríguez  Franck Audemard  Carlos Izarra  the BOLIVAR Active Seismic Working Group 《Journal of Geodynamics》2008,45(4-5):191-200

The Falcón Basin in northwestern Venezuela has a complex geological history driven by the interactions between the South American and Caribbean plates. Igneous intrusive bodies that outcrop along the axis of the basin have been associated with crustal thinning, and gravity modeling has shown evidence for a significantly thinned crust beneath the basin. In this study, crustal scale seismic refraction/wide-angle reflection data derived from onshore/offshore active seismic experiments are interpreted and forward-modeled to generate a P-wave velocity model for a 450 km long profile. The final model shows thinning of the crust beneath the Falcón Basin where depth to Moho decreases to 27 km from a value of 40 km about 100 km to the south. A deeper reflected phase on the offshore section is interpreted to be derived from the downgoing Caribbean slab. Velocity values were converted to density and the resulting gravimetric response was shown to be consistent with the regional gravity anomaly. The crustal thinning proposed here supports a rift origin for the Falcón Basin.  相似文献   

Effects of fish farm waste on Posidonia oceanica meadows: synthesis and provision of monitoring and management tools     

Holmer M  Argyrou M  Dalsgaard T  Danovaro R  Diaz-Almela E  Duarte CM  Frederiksen M  Grau A  Karakassis I  Marbà N  Mirto S  Pérez M  Pusceddu A  Tsapakis M 《Marine pollution bulletin》2008,56(9):1618-1629

This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows.  相似文献   

Testing Logselfsimilarity of Soil Particle Size Distribution: Simulation with Minimum Inputs     

Carlos García-Gutiérrez  Miguel Ángel Martín 《Pure and Applied Geophysics》2008,165(6):1117-1129

  相似文献   

Factors determining subsidence in urbanized floodplains: evidence from MT‐InSAR in Seville (southern Spain)          下载免费PDF全文

Ana Ruiz‐Constán  Antonio M. Ruiz‐Armenteros  Jesús Galindo‐Zaldívar  Francisco Lamas‐Fernández  Joaquim João Sousa  Carlos Sanz de Galdeano  Antonio Pedrera  Sergio Martos‐Rosillo  Miguel Caro Cuenca  J. Manuel Delgado  Ramon F. Hanssen  Antonio J. Gil 《地球表面变化过程与地形》2017,42(14):2484-2497

Major rivers have traditionally been linked with important human settlements throughout history. The growth of cities over recent river deposits makes necessary the use of multidisciplinary approaches to characterize the evolution of drainage networks in urbanized areas. Since under‐consolidated fluvial sediments are especially sensitive to compaction, their spatial distribution, thickness, and mechanical behavior must be studied. Here, we report on subsidence in the city of Seville (Southern Spain) between 2003 and 2010, through the analysis of the results obtained with the Multi‐Temporal InSAR (MT‐InSAR) technique. In addition, the temporal evolution of the subsidence is correlated with the rainfall, the river water column and the piezometric level. Finally, we characterize the geotechnical parameters of the fluvial sediments and calculate the theoretical settlement in the most representative sectors. Deformation maps clearly indicate that the spatial extent of subsidence is controlled by the distribution of under‐consolidated fine‐grained fluvial sediments at heights comprised in the range of river level variation. This is clearly evident at the western margin of the river and the surroundings of its tributaries, and differs from rainfall results as consequence of the anthropic regulation of the river. On the other hand, this influence is not detected at the eastern margin due to the shallow presence of coarse‐grain consolidated sediments of different terrace levels. The derived results prove valuable for implementing urban planning strategies, and the InSAR technique can therefore be considered as a complementary tool to help unravel the subsidence tendency of cities located over under‐consolidated fluvial deposits. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Cover Image          下载免费PDF全文

Dilce F. Rossetti  Rogério Gribel  Hanna Tuomisto  Carlos L.O. Cordeiro  Sonia H. Tatumi 《地球表面变化过程与地形》2018,43(6):i-i

  相似文献   

The role of armadillos in the movement of archaeological materials: An experimental approach     

Astolfo G. Mello Araujo  Jos Carlos Marcelino 《Geoarchaeology》2003,18(4):433-460

Armadillos are medium‐sized animals whose burrowing behavior can be significant in archaeological settings ranging from South America to the central United States. Although archaeologists are well aware that these animals can move archaeological materials across stratigraphic layers, few data are available about the magnitude of mixing, number of burrows per individual, dimension of burrows, and their impact on archaeological sites. This paper addresses the problem from an experimental perspective. Specifically, we monitored the action of the yellow armadillo (Euphractus sexcintus) in translocating cultural materials. Our results suggest that: (1) the vertical movement of artifacts has no preferential direction; (2) cultural horizons at least 20 cm apart can be mixed; (3) the animal's activity leaves some distinct traces that can be recognized during an excavation; and (4) there is no significant correlation between size, shape, or weight of artifacts and amount of displacement. © 2003 Wiley Periodicals, Inc.  相似文献   

Denitrification-nitrification process in permeable coastal sediments: An investigation on the effect of salinity and nitrate availability using flow-through reactors     

Shan Jiang  Mark Kavanagh  Juan Severino Pino Ibánhez  Carlos Rocha 《海洋学报(英文版)》2021,40(9):1-2

Permeable coastal sediments act as a reactive node in the littoral zone,transforming nutrients via a wide range of biogeochemical reactions.Reaction rates are controlled by abiotic factors,e.g.,salinity,temperature or solute concentration.Here,a series of incubation experiments,using flow-through reactors,were conducted to simulate the biogeochemical cycling of nitrate (NO_3~?) and phosphorus (P) in permeable sediments under differentNO_3~?availability conditions (factor I) along a salinity gradient (admixture of river and seawater,factor II).In an oligotrophic scenario,i.e.,unamendedNO_3~?concentrations in both river and seawater,sediments acted as a permanent net source ofNO_3~?to the water column.The peak production rate occurred at an intermediate salinity(20).IncreasingNO_3~?availability in river water significantly enhanced netNO_3~?removal rates within the salinity range of 0 to 30,likely via the denitrification pathway based on the sediment microbiota composition.In this scenario,the most active removal was obtained at salinity of 10.When both river and seawater were spiked with NO_3~?,the highest removal rate switched to the highest salinity (36).It suggests the salinity preference of theNO_3~?removal pathway by local denitrifiers (e.g.,Bacillus and Paracoccus) and thatNO_3~?removal in coastal sediments can be significantly constrained by the dilution relatedNO_3~?availability.Compared with the obtained variation forNO_3~?reactions,permeable sediments acted as a sink of soluble reactive P in all treatments,regardless of salinity andNO_3~?input concentrations,indicating a possibility of P-deficiency for coastal water from the intensive cycling in permeable sediments.Furthermore,the net production of dissolved organic carbon (DOC) in all treatments was positively correlated with the measuredNO_3~?reaction rates,indicating that the DOC supply may not be the key factor forNO_3~?removal rates due to the consumption by intensive aerobic respiration.Considering the intensive production of recalcitrant carbon solutes,the active denitrification was assumed to be supported by sedimentary organic matter.  相似文献